Hydraulically actuated pumping apparatus used downhole in a borehole for producing a wellbore generally includes a hydraulically actuated engine which reciprocates a piston associated with a downhole pump, so that production fluid is forced into the pump working chamber and then upwards towards the surface of the earth along with spent power fluid from the engine. Hydraulically actuated, downhole pumps are very complex in design and are usually made for operation in deep, slim boreholes.
In my previously issued U.S. Pat. Nos. 4,032,266 and 2,932,312, there is disclosed a check valve system for pumps which constitute an improvement over the Coberly U.S. Pat. No. 2,081,222. Reference is made to these previously issued patents for further background of this invention. In several of these previously issued patents, there is disclosed a valve structure in the form of a circular hub member, or valve plate, which has a plurality of exhaust and intake ports formed therein. The intake ports are formed therein by two intersecting constant diameter counterbores, with one of the counterbores being vertically disposed and located circumferentially spaced from the axial bore which receives the connecting rod therethrough, and with the other connecting counterbores being normally arranged and radially disposed respective to the first recited counterbores. The exhaust ports are located between the intake ports and extend parallel to the longitudinal axial centerline of the pump assembly. Opposed valve elements are biased into engagement with the exhaust ports located on one side of the valve plate and into engagement with the intake ports located on the other side of the valve plate. This configuration of a check valve assembly results in a cylindrical valve structure having coacting parts, some of which can axially rotate respective to the valve plate.
Further, in these and other prior art valve assemblies, provision must be made for the flow of formation fluid into the intake ports of the valve plate and the flow of produced fluid through the exhaust ports of the valve plate. Usually the fluid is conducted about an exhaust cage and then laterally into the inlet passageways of the valve plate. The passageways must be made as large as possible to enhance pump efficiency and to reduce fluid velocity, thereby avoiding damage to the valve plate interior by errosion resulting from debris admixed with the fluid. However, the fluid, as it flows to and from the valve plate ports, is forced to flow about a small annular area formed between the valve element and the intake or exhaust cage, so regardless of the improvements in pressure drop occasioned by the design of the valve plate, there remains a significant loss in efficiency because of the geometry of the valve elements and cages.
It is, therefore, desirable to provide a downhole, hydraulically actuated pump of a reciprocating type with improvements in the valve assembly associated therewith, which exhibits increased structural integrity along with improved flow characteristics, so that the life of the entire system is significantly prolonged, and overall pump efficiency is enhanced.